This application claims the priority of German Application 19914943.7, filed Apr. 1, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a reluctance motor with at least two salient stator poles each provided with an exciter winding, and to a method for the manufacture of the stator of such a reluctance motor.
Switching reluctance motors usually have numerous salient poles both in the stator and in the rotor. Each motor phase has at least one pair of stator poles lying diametrically opposite one another. An exciter winding is disposed on each stator pole. The two exciter windings on the stator poles are connected in series or in parallel. The stator and rotor poles consist of laminated sheet iron. When an exciter current is fed into the exciter windings, the stator poles are magnetized, so that magnetic attraction forces are exercised on the rotor, to thereby cause rotation.
The stator poles or stator teeth are integral components of the stator, i.e., the stator yoke and stator teeth consist of a single piece. The exciter coils are made self-supporting or they are held in coil boxes or coil frames. The self-supporting coils are wound on a form that can be taken apart, and after the removal of the form they remain held together, e.g., by tapes.
A reluctance motor is disclosed in European Patent EP 0 605 247 A2 wherein catch means are disposed at the axial ends of the spool bodies of the exciter windings, into which a stiff ring can be inserted. The coil bodies are fastened with the ring in the stator. A winding body serving as a coil box or coil frame supports the coil body.
A reluctance motor is disclosed in German Patent DE 42 20 209 A1, in which hollow cylindrical coil mountings are pressed on the inside of the heads of the coil windings in order to fasten the windings in the stator.
The exciter windings, constructed as independent units, are pushed over the stator poles or teeth and then fastened thereon. When current flows, radial forces are exerted against the coils. These forces must be absorbed by the fastening means. To fasten the coils wedges are driven manually into the gaps between adjacent coils so that the coils are clamped between the stator teeth. Such fastening by means of wedges is disclosed in German Patent DE PS 880 614. Then the gaps in the windings and the gaps between the stator teeth and the coils are filled with resin. The coils are securely and tightly bound to the stator in the manner described above.
Driving wedges between the coils is difficult and, especially in the case of a reluctance motor with numerous stator poles, it is very time-consuming. The coils are fixed in their position by pressing them onto the stator teeth. A resultant force acts on the coils which has an inwardly directed component. The friction between the coil and the stator teeth must be fairly great, since otherwise the coil is not firmly seated. Also, the coils take up part of the space between the adjacent stator teeth. This space is not available for the coil windings.
The invention therefore is addressed to the problem of preparing and manufacturing a reluctance motor with at least two stator poles each provided with an exciter coil, in which radial forces acting toward the stator yoke are exerted simultaneously on all exciter coils and hold the exciter coils in their positions on the stator poles.
The problem is solved according the invention, in a reluctance motor by using at least one snap ring springing radially outward with its outer side under spring bias against the sides facing the rotor of the exciter coils surrounding the stator poles or of their winding bodies. The snap ring exerts a force directed radially outwardly against the exciter coils. The force holds the exciter coils against the rotor yoke with their ends facing away from the rotor or facing towards the corresponding ends of the coil frame or coil box. The exciter coils are held fast between the snap ring and the yoke of the stator by the force from the snap ring, i.e., they are gripped between them. It is also possible to provide abutments between the ends of the coils or their frames or coil boxes facing away from the stator yoke and the rotor, against which the corresponding ends of the exciter coils or frames or coil boxes are then urged under the influence of the spring force. The installation of snap rings is a simple measure requiring but a few manipulations. The mounting of the exciter coils is thereby substantially simplified. After the exciter coils are fixed in their position with the snap ring, they can be filled with casting resin. Another advantage of the present invention is that the entire space between the stator teeth is available for the windings.
Preferably, a groove for the insertion of the snap ring is provided in the stator poles in or approximately in the center of the end facing the rotor. With this structure, the snap ring is also held in a simple manner in the axial direction of the reluctance motor.
In one preferred embodiment a snap ring is provided, axially of the stator, on each side of the stator teeth, and is urged against the end of the coil, coil frame or coil box facing the rotor. This embodiment is advantageous whenever the reluctance motor has a great axial length, because the force pressing against the coils is then more uniformly distributed.
The snap ring consists especially of a magnetic or nonmagnetic steel. Therefore no iron losses develop in the snap ring. Since the snap ring is not a full ring, the eddy current losses occurring in operation are of no importance.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.